1. Field of the Invention
The present invention relates to venetian blind components, and more specifically to adjustable tilt drums that regulate the angular adjustment of horizontal slats in a blind assembly. In particular, the invention features a polygonal tilt drum that provides for the improved closure of slats in a venetian blind, and accommodates the attachment of various kinds of ladder cords or tapes.
2. Discussion of the Prior Art
Venetian blinds have enjoyed widespread use as a decorative and functional solution for providing privacy and light control for windows. Typically, these coverings feature a sequence of horizontally oriented slats that are suspended beneath a headrail through the use of braided ladder cords or woven fabric ladder tapes. At least two ladders are required to assemble a blind, where more may be required depending on the overall width of the window covering, and the kind of slat material used within the construction. Each type of ladder includes a pair of vertically extending legs that are interconnected by a plurality of horizontal rungs spaced at regular intervals, which support and retain the slats in parallel fashion. The upper ends of each ladder are correspondingly attached to a tilt drum, which is carried on a tilt rod located within the headrail. The bi-directional rotation of the tilt rod causes the tilt drums to uniformly turn in response to the selective adjustment of the tilting mechanism. The reciprocating movement of each tilt drum will vertically raise one leg of each ladder cord or tape, while alternately lowering the corresponding leg of each ladder, thereby causing the attached rungs and slats to slant in relation to the vertical orientation of the parallel ladder legs. Accordingly, with this traditional assembly, the slats of a venetian blind may be opened, closed or adjusted to control privacy and the degree of light entering a room.
Usually, most prior art tilt mechanisms for venetian blinds utilize cylindrically shaped tilt drums, which have an attachment means for securing braided ladder cords, fabric ladder tapes, or are designed to accept the selection of either ladder style. Such pieces may be fabricated from metal stampings or, alternatively, may be formed from injection molded plastic. One of the known disadvantages of using these barrel-shaped components relates to their unfavorable effect in attaining uniform closure among the slats of a horizontal blind. This is due to the fact that when the suspended slats are adjusted into a fully closed position, the tilt mechanism winds the ladder cords or tapes around each tilt drum, thereby increasing their overall diameter. In this particular instance, the enlarged outside dimension of the tilt drum inhibits the full range of vertical motion in the uppermost segments of each ladder leg, thus limiting the effective closure of the top slat of an assembled blind. For blinds using ladder cords, this problem may be overcome through the installation of slat clips, which secures the uppermost slat into position with the first rung of a ladder cord, effectively holding the slat into position to follow the perpendicular movement of the ladder legs.
Another option for improving the closure of venetian type blinds has been disclosed by Tyner, in U.S. Pat. No. 6,622,770, wherein the profile of the tilt drum mechanism is generally elliptical or oval in shape. According to the invention, the contour of the tape drum causes the legs of the ladder to move in unison throughout the vertical length of the blind, and particularly in the region located closest to the top slat. However, the major diameter of this elliptically shaped tilt drum orients the significant weight of the suspended slats away from the central supporting axis of the tilt rod. This increases the load on the axial passage molded into the more slender region of the plastic component. Furthermore, this uneven weight displacement inhibits the smooth angular rotation of the slats as they are adjusted by the tilting mechanism.
Accordingly, it is an object of the present invention to provide a resilient tilt drum for venetian type blinds that improves the closure of suspended slats within such window coverings.
It is a further object of the invention to provide a tilt drum having a profile in the form of a polygonal structure consisting of a plurality of faceted sidewalls encompassing a central supporting tilt rod core.
It is yet another object of the invention to provide a tilt drum having inherent design features that facilitate the efficient attachment of ladder cords or, alternatively, ladder tapes of different dimensional widths.
Finally, an object of the invention is to provide a tilt drum having features that effectively counter balance the weight of suspended slats—to enhance the ease of operation—while additionally facilitating the efficient attachment of ladder cords.
These and other objects of the invention will be apparent to those skilled in the art from the following detailed description of the preferred embodiments of the instant invention.